Coupling Vibrations and Excitations: Exploring Ground-to-Excited State Relationships in Titania

Abstract

This work studies a plausible relationship between ground-state properties and excited-state ones of photoactive hydrated titania nanoclusters. The goal is to understand the effect of the hydration degree on the structural and vibrational properties and excitation energies of a series of (TiO2)16(H2O)n (n = 0, 1 ,2 ,3 ,4 ,5 ,6, 7 and 8) nanoclusters. This computational exploration involves classical molecular dynamics and time-dependent density functional theory calculations. The results reveal that hydration induces structural distortions reflected in the vibrational modes of the titania nanoclusters framework. These changes are introduced by hydroxyl groups derived from dissociative water interaction. The degree of hydration also influences the excited state properties, shifting the lowest excitation energies towards higher values. In addition, the temperature at which the dynamics are performed significantly affects both the vibrational modes and the evolution of the excited state energies with time. Overall, this study demonstrates that both hydration and temperature play decisive roles in defining excited-state transitions in titania nanoclusters. Shortly, by identifying the vibrational modes coupled to the first excitation energy, the present work provides insight into the interplay between structure, dynamics and electronic excitations in photoactive TiO2 nanosystems, offering valuable information for the rational design of efficient photocatalysts in aqueous environments.